Jack,

Whitner's collision with Pierre Thomas is a great example. If this rule were being contested before the Supreme Court, that is the play that should be argued. Because you're right, neither player was seeking to use their helmet as a weapon. On the contrary, both of them lowered their heads in that reflexive manner creatures adopt when they are trying to lessen the effect of an impact: they were basically shutting their eyes and looking away.

And yes, lowering the head, and shoulders, is to my mind so intrinsic to the basic effort of a ball carrier trying to deal with a tackle that it's almost impossible to think of it as a "dirty" maneuver. We might as well throw out most of Roger Craig's career, because he made the tackle zone perilous for defenders with his head as much as with his knees.

It's an awfully fine line to draw. On the one hand you can admire players like Sanders or Brown who claimed they never drove through defenders with their heads, but how can you not also admire any running back who runs low to the ground or effectively closes up the tackle zone by running into a crouch position with helmet and knees foremost?